This invention relates to aircraft toilets and, more particularly, to a pressurized drain for the waste holding tank of an aircraft toilet system.
Most airplanes presently in use have toilet systems which include an individual waste storage tank for each toilet bowl. A gravity drain is used to remove waste from the bowl and pass it to the waste storage tank. The individual waste storage tanks are then gravity-drained through openings in the skin of the aircraft during servicing of the airplane on the ground.
A more modern proposed toilet system for use in aircraft includes a vacuum flush system which drains waste material from the bowl to the remote waste storage tank by means of a partial vacuum maintained in the waste storage tank. In the majority of these systems a single waste storage tank is used to receive the waste material from several individual toilet bowls. Even though the waste is drained from the toilet bowl to the waste storage tank by vacuum pressure the servicing and emptying of the waste storage tank is still accomplished by a gravity drain through the skin of the aircraft.
The use of a gravity drain from the waste storage tank necessitates that the drainage opening in the waste storage tank be below the level of the waste therein. The location of the drain below the waste level makes the gravity drain system subject to leakage problems. For example, if the seal is deteriorated to any degree the waste material from the tank will leak around the drain seal. Leakage of the waste from the waste storage tank gravity drain is a major problem in commercial aircraft today. The leakage causes potential health hazards because of the waste material which is deposited in populous areas which otherwise would be contained within the waste storage tank. It also creates a hazard to the aircraft since in flight the liquified waste, after it leaks from the storage tank to the outer skin of the aircraft, tends to freeze into solid ice pieces which can break off and be drawn into the jet engine air intake or fall to the earth as large pieces of ice potentially causing damage to either persons or property.
It is therefore an object of the present invention to provide a drainage system for use in an aircraft toilet system which eliminates the need for a gravity drain.
It is a further object of this invention to provide a system in which the waste is drained from the tank under pressure thereby permitting the waste drainage passage to be dry during nonservicing periods.
It is another object of this invention to provide a pressurized drainage from a waste storage tank in a vacuum flush toilet system which eliminates leakage from the waste storage tank.
It is another object of this invention to provide such a drainage system which is easy to maintain and relatively economical to install.